Diagnostic value of diffusion weighted imaging on local recurrence of nasopharyngeal carcinoma / 中华放射学杂志

ABSTRACT

Objective To investigate the diagnostic value of DWI on nasopharyngeal neoplasm recurrence and fibrotic lesions after radiotherapy.Methods A retrospective analysis of pathologically confirmed nasopharyngeal neoplasm was performed in 39 patients with recurrent patients ( recurrence group ) confirmed by biopsy or MRI follow-up and 51 patients with confirmed localized fibrosis (fibrosis group) after radiotherapy.All patients underwent DWI , non-enhanced and enhanced MR scan.DWI findings and ADC values of the lesions in two groups of patients were observed and measured , then compared by using independent samples t test.Diagnostic performance of routine MRI and DWI in the diagnosis of nasopharyngeal neoplasm recurrence after radiotherapy was calculated by using ROC analysis and the differences of both of them were analyzed by using Z test.Results DWI of 39 recurrent patients showed hyper-intensity signal and ADC map showed hypo-intensity signal appearance.Overall signal of DWI in 51 recurrent patients is lower than that in recurrent group , in which ADC maps of 36 cases showed iso-intensity or moderately hypo-intensity signal appearance and the remaining 15 cases showed moderate hyper-intensity signal appearance.The ADC values of recurrent group and fibrotic group were (0.753 ±0.127) × 10 -3 mm2/s, and ( 1.233 ± 0.310 ) ×10 -3 mm2/s, respectively.The difference was statistically significant ( t=-9.118, P<0.05).On the ROC curve, the sensitivity of ADC for the diagnosis of tumor recurrence was 87.18%(34/39), specificity 94.12%(48/51) and area under the ROC curve 0.968 with the ADC cutoff value of 0.887 ×10 -3 mm2/s.The sensitivity of routine MRI was 71.79% ( 28/39 ) , the specificity 74.51% ( 38/51 ) and the area under the ROC curve was 0.732 for the diagnosis of tumor recurrence.The difference of area under the curve between them was statistically significant ( Z=4.583, P<0.01).Conclusion DWI can help tumor detection and diagnosis of recurrent nasopharyngeal neoplasm and has a higher diagnostic performance compared with routine MRI.